Guarding a scepter Isle

Rising water levels are one of the most potent threats posed by global warming. In response Britain has double its spending on flood prevention. The most visible evidence of the danger is the tames barrier, a set of hulking yet beautiful flood gates that bisect the waterway 11miles downriver from central London. When the barrier became operational in 1983, 30 years after the massive flood that spurred its construction, planners expected that it might have to close once or twice a year to keep ocean storm surges from inundating the capital. In the past decade, however, extreme weather has caused the barrier to be closed and average of 10 times each year